Wireless mobile communication networks continue to evolve given the increased traffic demands on the networks, the expanded coverage areas for service and the new systems being deployed. Cellular (“wireless”) communications networks rely on a network of base station antennas for connecting cellular devices, such as cellular telephones, to the wireless network. Many base station antennas include a plurality of radiating elements in a linear array. Various attributes of the antenna array, such as beam elevation angle, beam azimuth angle, and half power beam width may be adjusted by electrical-mechanical controllers. See, for example, U.S. Pat. Nos. 6,573,875 and 6,603,436, both of which are incorporated by reference. However, the known electrically-driven phase shifters tend to suffer from complicated linkages, can typically be driven only from one end, and would require substantial engineering to adapt from one antenna design to another.
Additionally, the presence of the phase shifter assemblies in coaxial cable fed assemblies also typically means that a large number of solder joints are present. Base station antennas require many soldered joints where coaxial cable is fastened to printed circuit boards (PCBs). Many of these soldered joints involve connecting coaxial cables to phase shifter PCBs. The solder joints between coaxial cables and PCBs are susceptible to damage unless the joint is protected by a strain relief. Known strain relief structures included metal cages that guided the coaxial cables to the phase shifter PCBs. However, such strain relief was applied after the solder joint was made, thereby allowing a period of time when the solder joint was susceptible to damage.
The solder joints within the base station antennas are susceptible to damage from multiple sources. The normal movements of the cables when being dressed into their final positions during assembly can place stress on solder joints. The solder joints may be damaged during installation of the base station antenna. Solder joints may also experience damage in the field from vibration during normal operation, or as a result of weather or other external forces. Damage to the solder joint can lead to undesirable passive intermodulation (PIM) effects in the antenna transmission characteristics. Therefore, it is an object of the present invention to provide an efficient means to secure coaxial cable within base station antennas such that damage to solder joints is minimized.
The mechanical failure of solder joints in a phase shifter assembly adds to the cost of producing an antenna panel. This is especially true when the solder joint failure is not detected until after the antenna panel has been assembled. Solder joints have been known to have been mechanically compromised by simply moving a known phase shifter assembly from an assembly station to a test station.
Previous methods of coaxial cable management include use of a rigid clamp for holding the cable in the cable housing. This previous method suffers from several deficiencies. First, the diameter of common coaxial cables is subject to typical manufacturing tolerances. A rigid clamp manufactured to a specific size is often too large to secure a coaxial cable, because rigid clamps must be designed to accommodate the largest cable diameter within a given tolerance. Second, a rigid clamp does not address the problems associated with damage to solder joints due to vibration. As explained above, it is common for base station antennas to experience vibration from normal operation, or as a result of weather or other external forces. Rigid clamps do not reduce the effects of vibration of the base station antenna housing. Finally, another previous method for coaxial cable management uses a rigid clamp affixed by screws, bolts or other attachment means. For example, U.S. Pat. No. 5,411,228 to Morawa et al. discloses a cable clip having a cylindrically-shaped fastener hole for frictional engagement with the fastener device. In addition to suffering from the same deficiencies as the basic rigid clamp, the rigid clamp affixed by screws has the disadvantage of extra parts and increased cost.